Investigators are searching for the suspect who shot and killed a federal agent outside a busy South Florida post office.

Authorities say 52-year-old agent Donald Pettit was with his 12-year-old daughter when he was shot by a man during some sort of fight Tuesday morning in the post office’s parking lot.

The gunman took off after firing at least one shot. No one else was injured.

Pettit’s widow pleaded with the public for help Wednesday in finding the suspect. A reward for his capture has been increased to $275,000.

Authorities are looking for a man described as between 50 and 60 years old, six feet tall, medium to heavy build, with gray and white bushy hair and “distinctive sagging cheeks.”