The man who shot and killed five residents in a quiet neighborhood in Lake Havasu City Aug. 28 before taking his own life hours later in California, first appeared on local police radar in 2006.

Since then, a string of reports filed against him, citations and arrests plagued 26-year-old Brian Diez’s past and quickly tarnished his reputation in the boating industry.

“It’s possible that his business transactions and his methods of doing things kind of spiraled downhill,” said Lake Havasu City resident George Shilala Jr. “He may be a real nice guy, but we are not going to know that.”

Shilala Jr. is just one of several local accounts of Diez’s questionable business practices that augment the police paperwork filed on him. The earliest complaints filed in 2006 at the Lake Havasu City Police Department allege Diez stopped making payments on a motorcycle and another states that a man bought two gas tanks from Diez and never received them.

But from there the short police reports quickly get longer and more severe. Traffic citations of speeding, driving with suspended license plates and with a suspended license dot the more common allegations that Diez would sell boating equipment online, receive payment, and then never ship the products.

In 2007, a complaint was filed that Diez stole a super charger kit from a boating company that he worked for at the time. An employee of the company, who declined to give his name, said Diez returned the kit and charges were never filed.

Bart Bennett, a service manager at Alco Marine Sales and Service, said Diez also took a super charger when working for Alco later. Alco was not the company that filed the first super charger complaint against Diez. Bennett said super chargers help increase boating horsepower and cost between $5,000 to $10,000.

“He only worked here for a short time because he wasn’t a good employee,” Bennett said. “And we couldn’t trust him. Almost to the day he started, he was selling parts over the Internet. It was bad. It was like we couldn’t have a guy like that work for us.”

Bennett said Diez worked for Alco for a few months and was “forced” to return the super charger. He said about a week or two after Diez started his employment there, people would call the business looking for him.

“I don’t know how they found out he was working here,” Bennett said.

Shilala Jr. said he is a member of several online performance boating sites, and between eight to 10 people — both local and out of state — contacted him requesting his assistance to help them receive the parts they had bought from Diez online.

“I’m shocked at how it happened, but I’m not surprised that he was involved (in the shooting),” Shilala Jr. said. “I would have expected, honestly, that someone that he would had done business with would have come after him.

”It’s very sad,” he continued. “Obviously, he was a smart guy. He was able to work on boats and do things and to spiral down like this and take everybody else with you … such a waste of life.”

In February 2008, the Arizona Corporation Commission approved the formation of a new local business, Redline Speed & Marine Inc. Online documents show Diez as one of the directors. The address listed matches an address on one of Diez’s police reports.

The incorporation document also lists Steve Astorga as director and Rhonda Russell, of Lake Havasu City-based Russell Financial and Business, as the agent.

Astorga or Russell could not be reached for comment.

The online documents state the business was dissolved in August 2009 after the failure to file an annual report.

About seven months after the company formed, Diez was arrested on theft in August 2008 after passing a $233 check for valve covers from a closed bank.

That same month, Diez was arrested on a warrant after a police responded to a domestic violence call for service (no arrest was made in connection to the call). Police, however, did remove 10 rifles, shotguns, and handguns from the property for “safekeeping,” according to the report.

A civil complaint then filed with the local police department in September 2008 states: “Astorga went into business with (Diez). Astorga is unhappy with (Diez) and thought there (were) some illegal business practices taking place by (Diez). Investigation revealed no illegal activity.”

In December 2008, another police complaint was filed alleging that Diez still owed a man a “prop” that he purchased in 2006 and never received. The complaint states that Diez said he would return the man’s money.

The police report that prompted 23-year-old Deborah Langstaff, the mother of Diez’s children and with whom he was in a long-term relationship, to seek an order of protection against Diez emerges in February.

Langstaff was one of the five people murdered Aug. 28. After the shooting, Diez took the couple’s two children, 13-month-old Cole Diez and 4-year-old Kaia Diez, to his sister’s house in Rancho Cucamonga, Calif. He left them unharmed at the door before walking to his truck and shooting himself.

Close friends of Langstaff said Friday the children were safe with family who would raise them. They declined to state which family member will seek custody of the children.

The report states that Diez did not work and Langstaff worked 13-hour shifts.

Langstaff was a nurse at Havasu Regional Medical Center. The report stated that Kaia would attend daycare during Langstaff’s working hours and family members would watch Cole. The report states that the family was eating dinner on Feb. 8 when [redacted] stated that Diez had “slapped [redacted] earlier in the day.” [Redacted] also stated that Diez did not take her to school.

“[Redacted] is three and sometimes makes up stories, but never anything serious,” the report stated.

After eating, Diez and Langstaff checked on the baby when Langstaff noticed a mark on his cheek. She photographed the infant. Diez denied striking the child, according to the report. Langstaff asked Diez to leave, which he did, and the next day she sought an order of protection against him prohibiting him from seeing the children and requesting exclusive use of the residence in the 300 block of Opossum Drive, where the shooting occurred.

“Brian has been physically violent with her in the past and has a bad temper,” the report states. “She has suspected him of possibly hurting [redacted] once when she was about [redacted] age, and it was investigated by CPS, but was unfounded,” the report states.

In April, Diez was then charged with one count of domestic violence/assault in relation to the February incident. In June, Diez was again arrested and charged with theft.

An Iowa man alleged he bought a 1971 Chevrolet Chevelle for $5,000 from Diez on craigslist.org. The report states the man paid a trucking company $700 to transport the vehicle, but the trucking company never contacted Diez.

The man then stated he tried to arrange transportation of the vehicle with Diez after the first of the year, but was told via e-mail that Diez was “out of the country.”

The man then drove 1,500 miles to Lake Havasu City to the Opossum Drive house looking for Diez and the vehicle. No one was at the residence, the report states, and the man requested police assistance.

Police found Diez and he told them that he had sold the car to someone in Parker for $5,000 and did not inform the Iowa resident that he had re-sold the vehicle, the report states. Diez also said he never sent the Iowa resident his money back and that “he no longer had the money to return to him.”

On Aug. 13, — almost two weeks before the shooting — police arrested Diez for violating his order of protection Langstaff, who was out with friends that evening, alleged Diez texted her stating: “I have something that is very very important to give you. It can’t wait [redacted] please call me.” Langstaff ignored the message, according to police, but soon after discovered his vehicle parked next to hers at a local movie theater. She called a friend to pick her up and went to a bar at a resort in the 100 block of North McCulloch Boulevard, where Diez again was spotted on the balcony.

The last criminal entry listed in the Lake Havasu City Police Department summary is on Aug. 28: homicide.

Diez entered the home around 11:50 p.m. Saturday and opened fire with a semi-automatic handgun that killed Langstaff, 20-year-old Broc Kelson; Primo Verdone, 24; Russell Nyland, 42; and Ashleigh Nyland, 20. Debbi Nyland, 44, the sole survivor, is in good condition in a Las Vegas hospital.

She was Russell’s wife and Ashleigh?s mother.

Langstaff and Verdone had just started dating and police have said the gathering could have been to celebrate Verdone’s birthday that day.

“I can’t say that it was shocking,” Bennett said. “I didn’t know that he would ever do something like this. I would think more someone would have come and took him out just because of the dealings. What he did was just incomprehensible. I don’t know how else I put it nicely. It’s just so tragic.”

You may contact the reporter at jleatherman@havasunews.com