Imani Rashad Lee had no criminal record and nothing in his past that made the owner of Trojan Alarm Solutions Inc. think twice about hiring him.

The owner of the Hanover business certainly never anticipated that the 30-year-old's angry, erratic behavior on his first day of work would set off a chain of events ending with him being shot and killed by county police Monday afternoon.

Police shot Lee after he punched and stabbed an office-supply salesman who stopped by the business to drop off pamphlets. Lee held the 26-year-old Baltimore County man hostage for about 20 minutes and stabbed him with a box cutter before police...