A grand jury voted not to indict a White Plains police officer who shot and killed a 68-year-old former correction officer and former Marine in his apartment last November, the Westchester County district attorney said Thursday.

District Attorney Janet DiFiore called the shooting “a tragedy on many levels.” But she said the grand jury had concluded that “there was no reasonable cause” to indict Officer Anthony Carelli, who fired the shot that killed the victim, Kenneth Chamberlain Sr.

Officer Carelli and several other officers were sent to Mr. Chamberlain’s apartment after his medical-alert pendant went off and he did not respond to a call from a medical-alert agency operator.

After Ms. DiFiore announced the grand jury’s decision, the White Plains police released more than 200 pages of documents about the encounter, along with audio and video recordings made as it unfolded. In one report, Officer Stephen Demchuk described Mr. Chamberlain as “acting irrational” when the police arrived and said he stuck an eight-inch butcher knife through a crack in the door.