'I couldn't just stand by and watch my neighbor die senselessly': Armed citizen ends grisly rampage

 Around 12:30 p.m. on August 12, in Mesa, Arizona, Emmanuel Reynoso Avila ran into his home to grab his gun. He had just witnessed a man hit his next-door neighbor Christopher Heimer, 63, with his vehicle.

Heimer was walking along the sidewalk near Main Street and Power Road. Allegedly, 61-year-old John Lagana — who had been honking his horn incessantly in the parking lot northwest of Heimer's house in hopes of drawing out the victim — accelerated through the lot and onto the road. The Mesa Police Department said in a release that Lagana then swerved out of the roadway and struck Heimer, launching him into the area in front of a four-plex apartment building.

Avila told KNXV that after hearing the car speed up, he saw his neighbor "get full on rammed by someone who was supposedly his friend. ... We saw Chris fly through the air. We saw him land. He was unresponsive." 

"I couldn't just stand by and watch my neighbor die senselessly," Avila told reporters. While his brother called first responders, Avila ran into his house to arm himself. Meanwhile, the suspect continued his attack.

With the victim lying injured on the ground, Lagana is reported to have continued driving eastbound on the sidewalk, smashing mailboxes and damaging property. Witnesses told police that Lagana then turned around and targeted the victim a second time.

After running over Heimer once again, Lagana allegedly exited his vehicle and began stomping on the victim's head.

Avila said that when the suspect got back inside his vehicle, ostensibly to flee the scene, he approached Lagana with his gun drawn. "I yelled 'Get out of the car.' I shot a warning shot, just to let the guy know I was serious." Avila held Lagana at gunpoint until police arrived.

Despite efforts by Mesa Fire and Medical, Heimer was pronounced dead on the scene.

Lena Santonocito, a friend of the deceased, said, "He was a good man. He was a good father. He was a good husband. He was a good friend."

Although it has been suggested that the suspect targeted Heimer over a parking dispute (Heimer had permitted Lagana, who was homeless, to park his car on his property), Lagana hinted at another possible motive. He reportedly stopped answering detectives' questions after revealing that he had recently learned that his ex-girlfriend was living at the victim's house.

Lagana has been charged with first-degree murder and is set to appear in court on August 18.

Armed neighbor detains murder suspect accused of repeatedly running over man in violent attackYouTube - KSAZ-TV