The basic sequence of events was this. Police had search warrants to raid Maye's apartment and that of his neighbor (two halves of a duplex) on suspicion of possession and dealing of drugs. The neighbor complied and allowed police to enter. Maye did not respond when police arrived at his apartment, so they forced their way through his back door. When an officer entered the apartment, Maye fired three shots, one of which struck and killed the officer.

The details of the events, of course, differ significantly. Here is Maye's account (taken from Balko, who got it from a TalkLeft blog post, which apparently excerpted it from a local newspaper):

Cory Maye, 23, said he was asleep on a chair in the living room of his Prentiss apartment as his 14-month-old daughter slept in the bedroom when he heard a loud crash at his front door. "I immediately ran to my daughter's room, got a pistol, put in a magazine and chambered a round," said Maye, who is on trial for capital murder in Marion County. "As I laid on the floor by the bed, I heard kicks at the back door. I was frightened, I thought someone was trying to break in on me and my daughter."

Maye testified that it was dark in his apartment when he heard someone breaking into the back door, which was located in the bedroom. "That's when I fired the shots," Maye said. "After I fired the shots, I heard them yell 'police! police!' Once I heard them, I put the weapon down and slid it away. I did not know they were police officers."

Here is prosecuter Claiborne "Buddy" McDonald's version of the events:

The warrants were served at the same time by two teams. The testimony was that there were several announcements that they were the police and that they had a search warrant. The occupants in the apartment next to Maye's allowed entry after announcement and there was no resistance. Maye did not. Porch lights were on in the front of Maye's apartment and the uniformed officers and marked cars visible in the front yard and on the porch. The officers announced at the front door and then at the back door. The officer who killed was at the front door initially and then went around the back to the back door before entry was made.

Obviously, a great deal hinges on whether the police announced themselves and allowed Maye enough time to respond peacefully. Balko is very skeptical of the surviving officers' claims that they announced themselves. I'm a little more skeptical of Maye's version of the events, although it's certainly possible that the truth has been obscured due to the tension and confusion of the situation. Even if Maye did not knowingly kill a police officer, I think he had the responsibility to warn a perceived intruder that he was armed before firing. (I also wonder what those who are defending Maye think about the Amadou Diallo case, wherein officers testified they believed Diallo was threatening their lives by reaching for a weapon in his jacket.)

What I do agree with Balko on, however, is that insufficient evidence was obtained to justify a late-night raid on Maye's apartment. Balko is working on a paper about "paramilitary-style" police raids where police gain the element of surprise against suspects by giving little or no warning before bursting into a residence. It's not clear to me whether Balko thinks such raids are ever warranted. I think there are cases where they are, but there must be convincing proof that the targeted residence is a base of illegal activity and that there is no other feasible way to apprehend the suspects and preserve evidence.

Here, again, is the link to the category page that contains all of Balko's writing about the Maye case.