Police in Chandler, AZ are releasing details on a shooting that happened early Saturday morning inside a local Walmart which left two police officers injured and a lone gunman dead.

Police Detective Seth Tyler called the shooting an “ambush.”

The Arizona Republic reports:

“When the first officer walked into the store, the suspect began firing at the officer immediately,” Tyler said, adding that police did not say how many shots were fired but did confirm the first officer was struck in the head. “You can call it what you want. It sounds like an ambush to me.”

Tyler said it’s unclear if the first officer was able to return fire, but said the second officer who responded shot and killed the man, later identified by police as Mitchell Oakley, 24.

Oakley, described by police as a transient with family ties to the area, was recognized as a trespasser in the Walmart by an employee who called police.

The employee did not mention Oakley possessing a firearm or having erratic behavior but did mention he had previously trespassed there, according to Tyler.

Witnesses told police that Oakley began firing multiple shots at the officers as soon as they entered his sight, said Chandler Police Chief Sean Duggan.

“A seemingly routine call turned into a deadly encounter within a split second,” Duggan said. “At that point, the officers drew their guns and they shot and killed the suspect.”

Tyler confirmed Oakley’s criminal history; online records from the Arizona Department of Corrections shows he was most recently released from the prison system in March 2015 for a 2013 conviction for destruction of a public jail.

Oakley was previously convicted in 2011 of aggravated assault, for which he served a year in prison. He was also convicted in 2012 for unlawful use of means of transportation, for which he served a 1½-year sentence.

Chandler officials said the officers received multiple gunshot wounds. They are both in stable condition.