CHICAGO (CBS) — The trial of an accused cop killer got underway Monday with emotional and graphic testimony.

Chicago Police Officer Nathaniel Taylor, 39, was gunned down while assisting with the execution of a search warrant on Sept. 28, 2008.

Lamar Cooper, 40, is charged with first-degree murder, accused of killing the 14-year police officer when Taylor and a team of drug officers tried to serve Cooper with a search warrant.

CBS 2’s Mai Martinez reports Taylor’s partner, Lem Miller, fought back tears as he testified about seeing Taylor get shot in the head, chest and arm as he walked up to Cooper’s car.

Taylor and Miller were assigned to conduct surveillance on Cooper’s home on the morning of Sept. 28, 2008, in preparation for a team of officers to serve a search warrant on the home at 7 a.m.

lamar cooper 0123 Trial Underway For Man Charged With Killing Cop In 2008

Lamar Cooper is charged with first-degree murder in the shooting death of Chicago Police Officer Nathaniel Taylor in September 2008. (Credit: Cook County Sheriff's Office)

When Cooper pulled up in front of his house around 5:30 a.m., Taylor and Miller were told to detain Cooper to keep him from entering his home, as police believed there were weapons, dogs and children inside.

Miller testified that, as Taylor approached Cooper’s car, Taylor identified himself as a police officer. The next thing his partner heard was two or three rapid shots. Then he saw Taylor go down.

Miller said he drew his gun and fired at Cooper 10 times, hitting him nine times before calling for help on his radio and checking on Taylor.

Taylor, 39, died hours later during surgery at Advocate Christ Medical Center in Oak Lawn.

Defense attorneys have not denied their client fired shots that night, but they said Cooper did so in self-defense because he thought he was being robbed and had no idea Taylor was a police officer.

Some of Taylor’s friends and family were in the courtroom Monday, but they were too emotional to talk about the case.

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