© Los Angeles Times via Getty ImagesThe Los Angeles County Probation Department was "currently investigating" why the suspect was not taken in for the violation.
Justin Flores, 35, allegedly slayed El Monte Police Cpl. Michael Paredes and Officer Joseph Santana and was killed in the firefight when the officers responded to a report of a stabbing.
Flores had served two prison terms for burglary and car theft and pleaded no contest to possessing a firearm as a felon last winter, according to The Los Angeles Times.
The weapons charge could have sent the career criminal back to prison for three years, but instead he was sentenced to two years' probation and 20 days of time served, the paper said.
A day before the shooting, Flores' probation officer filed for a revocation hearing after the suspect allegedly assaulted his girlfriend last week, violating his probation, according to the report.
Instead of being arrested and jailed, Flores was allowed to stay on the streets ahead of a June 27 hearing.
The Los Angeles County Probation Department was "currently investigating" why Flores was not taken in for the violation, the outlet said.
Paredes and Santana reportedly came under fire after knocking on the door of a room at the Siesta Inn Tuesday afternoon.
A shootout with Flores started in the room and ended in the parking lot with all three men dead, officials told the paper.
Flores reportedly followed his wife Diana Flores to the hotel, where she booked a room to escape him after he stabbed her a day earlier, according to NBC Los Angeles.
Police arrived shortly after Flores found his wife at the motel.
Diana Flores said she warned the officers that her husband was not in the right state of mind and had a gun.
"I love my husband to death but ... this wasn't my husband. This was a monster," Diana Flores said.
"I didn't want anyone to get hurt in this," she told NBC. "I am so deeply sorry. They didn't deserve that, or their families. They really didn't. They were trying to help me."
She said she fled the room as the two cops arrived and soon heard gunshots, so she ran.
"We don't have all the facts yet," El Monte Mayor Jessica Ancona reportedly said Tuesday night, adding the officers were "essentially ambushed."
The officers were native to the San Gabriel Valley city of 110,000 and were remembered by Ancona as hometown heroes.
"They grew up here; to us, they're El Monte homegrown," Ancona said. "They're our boys."
"They were good men," Capt. Ben Lowry, the El Monte Police Department's acting chief, told the paper. "These two heroes paid the ultimate sacrifice today. They were murdered by a coward."
Santana, 31, was survived by his wife, daughter and twin boys.
Paredes, 42, a 22-year veteran, left behind his wife, daughter and son.
A police station memorial adorned with candles, flowers, US flags and "thank you" signs was flooded by community residents.
Only two members of the department had ever died in the line of duty before Tuesday, the Times reported.
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