The man who was shot by police Thursday night in Aurora may have discovered he was under surveillance just before he was killed in front of his mother’s home.

Sgt. Cassidee Carlson, Aurora police spokeswoman, said Richard Arreola, 25, was being investigated for allegedly selling drugs out of a phone shop he owned.

Officers planned to execute warrants on Friday, but were keeping an eye on Arreola in the meantime.

When Arreola arrived at 1429 Macon St., an undercover officer watching the house said over the radio that his cover had been blown, and indicated that Arreola had a gun.

The undercover officer fired at Arreola multiple times through his car windshield just after 8:30 p.m.

Arreola did not open fire but police say he was walking “with purpose.”

Arreola was pronounced dead at the scene and was found with a revolver in his right hand, and a rifle just a few steps away.

Carlson said the investigation began when seven students from South Middle School in Aurora were caught late last week using or dealing meth after two of the middle schoolers were hospitalized.

“The narcotics unit jumped on it because it did involve middle schoolers,” Carlson said. “Arreola quickly became a suspect.”

Carlson said police had made a successful undercover purchase of marijuana at Arreola’s business and on Thursday had gone to a judge to obtain a search warrant in the case.

The warrant was executed Friday afternoon at Arreola’s business, Neviah Wireless on Peoria Street in Aurora. Police seized one pound of marijuana and two guns.

Friday afternoon, friends and neighbors gathered around the spot on the sidewalk where Arreola was shot, staring in disbelief at the snow spackled with blood.

Arreola’s family said Arreola had just arrived at his mother’s home to pick up his 3-year-old daughter.

Ruben Montano, Arreola’s younger brother, said he knew something was wrong when he heard seven gunshots.

“I went to go find him,” Montano said. “Then I saw my brother shot for no reason.”

The name of the of the officer has not been released. Following protocol, the officer was placed on administrative leave, pending an internal review.

Police said it is possible other people are involved in the drug incident involving the students, but the investigation is still ongoing.

Colorado Bureau of Investigation records show that in addition to several traffic offenses in Denver in 2008, Arreola was arrested on a misdemeanor marijuana possession charge. Arreola also served 18 days in jail and a year of probation for a gambling offense in 2007 out of Gilpin County.

In 2004 Arreola was named a Senior Youth Honoree at the annual Boys and Girls Clubs of Metro Denver Youth of the Year event. Honorees are selected based on efforts in leadership, academic achievement, community service and overcoming obstacles.

Yesenia Robles: 303-954-1372 or yrobles@denverpost.com