Shortly after a man was stabbed Thursday around 4:30 p.m. at 138 Tremont St., police saw the suspect walking in another part of town and arrested him and the person he was with. Back at the scene they arrested two others. 

According to police reports, Tad Helin, 20, of Boston, had become involved in an fight with Shawn Cagnina, 19, of Boston, Kayla Zadrowski, 23, of Lawrence and the victim. Helin was being punched and kicked, then pulled out a knife and stabbed the victim in the lower back. He fled toward North Station. 

Meanwhile, back at the scene the victim was transported to Tufts Medical Center for injuries police said were not life-threatening. 

An officer spotted Helin and another man, Jesus Rodriguez, 30, of Boston, walking on Friend Street, toward Rip Valenti Way. While handcuffing Helin, the officer saw Rodriguez discard a knife, according to reports. The officer retrieved the knife and arrested Rodriguez. 

Both Helin and Rodriguez were taken back to 138 Tremont St., where they were positively identified by Cagnina, Zadrowski and witnesses. 

Helin was arrested on a charge of assault with intent to murder; Rodriguez was arrested on a charge of possession of a dangerous weapon; Cagnina and Zadrowski were both arrested on a charge of assault with a dangerous weapon (shod foot); and the victim will be summoned to court on a charge of assault with a dangerous weapon (shod foot).