ALHAMBRA — Police arrested a transient Thursday on suspicion of stabbing another man in an unprovoked attack outside a coffee shop, authorities said.

Richard Covarrubias, 26, was booked on suspicion of assault with a deadly weapon in connection with the 5:08 p.m. attack outside a Starbucks coffee shop in the 100 block of West Main Street, Alhambra police Lt. Jennifer Wiese said.

A 43-year-old man was standing outside the coffee shop when he was approached by Covarrubias, who challenged the victim to fight, the lieutenant said.

The victim told police he had seen the man before, but did not know him or why he wanted to fight, Wiese said.

Covarrubias then pulled a knife and stabbed at the man, she said, inflicting a 4-inch gash to the victim’s hand.

The alleged attacker fled the scene before police arrived, but officers found him during a search of the area, police said.

According to county booking records, Covarrubias was being held in lieu of $30,000 bail pending his scheduled arraignment Monday in Alhambra Superior Court.