A customer at the U.S. Post Office in Colesville stabbed a fellow patron Thursday afternoon after he mistakenly thought the man had cut in line, Montgomery County police said.

Police said the victim, a 58-year-old man, was at the counter when he was asked to step aside to complete some paperwork. When the employee at the counter gestured for him to return, police said, a 67-year-old man who had been waiting thought the victim had cut in line.

The older man waited in the vestibule for the 58-year-old to leave, police said, and then attacked. Two women postal workers came to the victim’s aid, and at least one the women deployed pepper spray to subdue the attacker, police said.

Police said the stabbing occurred around 2 p.m. at the post office at 13217 New Hampshire Ave.

Police said the man who was stabbed was taken to an area hospital and was in serious but non-life-threatening condition. They said the 67-year-old was taken into custody. Police did not immediately name the suspect because he had not been formally charged.

Police are asking anyone who witnessed the incident to contact the 3rd District Investigative Section at 301-565-5835.

This post has been updated.