Three men have been arrested, but a fourth remains at large after a brutal stabbing just outside a Walgreens store on a Union Square Street.

San Francisco Police Department spokesperson Sergeant Monica MacDonald says that at around 2 a.m. Wednesday, four young men approached a security guard at the Walgreens store at 135 Powell Street, which is open 24 hours a day.

The men, MacDonald says, began to argue with the guard in the doorway of the store. According to KCBS, "Police said it appears the suspects had a dispute with a Walgreens employee working at the store on Powell Street, then returned to the store early Wednesday morning."

The altercation quickly escalated, as one of the suspects indicated that he was armed with a handgun, and another punched the guard.

Seeking to assist the besieged guard, additional Walgreens staffers rushed out of the store. That's when MacDonald says, "one of the suspects pulled out a knife and stabbed one of the employees several times in the upper body."

“The Walgreens employee was injured with multiple stab wounds to the body area,” SFPD Lt. Gaetano Caltagirone told KCBS, and “the security guard was assaulted."

SFPD searched the area following the scrum, and were able to track down three of the teens allegedly responsible, while the fourth remains free at publication time. Police also recovered the gun one of the suspects was allegedly carrying during the altercation.

One of the three arrested is a juvenile, so police won't be sharing any information on him. San Francisco residents Damareay Mitchell (age 18) and Antonio Rosales (age 19) were both arrested for attempted homicide, conspiracy, possession of a concealed firearm by a prohibited person, carrying a concealed weapon, possession of stolen property, possession of a stolen firearm, carrying a loaded firearm, and possession of a firearm in a public place.

One of the suspects also had a stab wound to the neck area, Caltagirone told KCBS. Both he and the injured Walgreens employee were transported to San Francisco General Hospital, where they are in stable condition.

The remaining suspect is described as an 18-20 year old man of unknown race, wearing dark clothing. Say it with me, folks: if you have any information on this crime, or the whereabouts of this suspect, you're encouraged to call SFPD's Anonymous Tip Line at 415-575-4444 or to send a text to TIP411 with SFPD at the beginning of the message.