Trivia: The film has eighty speaking parts.
Trivia: Had the film been successfully adapted into a TV series, Jack Vincennes would have been played by Kiefer Sutherland. Coincidentally, one of Sutherland's co-stars in The Sentinel (2006) is Kim Basinger, who won an Oscar for her role in this film; James Cromwell played his father in season six of "24."
Trivia: Kim Basinger won the Academy Award for Best Supporting Actress for her role as Lynn Bracken, even though she's only in the film for 15 minutes.
Chosen answer: A 12g shotgun blast at that range would cause an incredibly bloody death, especially as there is a good chance it hit the man in the face. Exley has killed a person in the line of duty before this, but not in such a spectacular way. And while he may not have meant to kill him he chose to shoot over letting the man escape.
Grumpy Scot
The scene was building up tension beyond "Will Ed catch the Night Owl suspect?" Ed has lost his glasses and gets to the elevator as the doors close. He fires blindly into the elevator; for a split second, Ed took a risk: he could've shot an innocent bystander. His career flashes before his eyes. IIRC, it was filmed in a way to imply Ed didn't actually see the suspect get in the doors. The doors open. Ed realises the risk was worth it. This is a pivotal point in his character development.