PORTLAND, Ore. (AP) — A gunman opened fire outside an under-21 nightclub in Portland, Ore., killing two girls and wounded several other people in an apparently random act of violence, police said.

Five victims were students from other countries and another was a Portland resident planning a trip as an exchange student; they were going to The Zone club to celebrate a birthday.

The man did not have any known relationship to the victims beforehand, and he didn’t appear to have been in the club or a nearby bar before the shooting Saturday night, police Detective Mary Wheat said Sunday.

Police late Sunday identified the alleged gunman as Erik Salvadore Ayala, 24.

He was in critical condition after shooting himself in the head, Wheat said.

‘‘At first blush, this incident appears to be a random act of violence, of the kind that makes you despair for America,’’ police Chief Rosie Sizer said.

Most of those shot were on the sidewalk outside The Zone but it was unknown if they were waiting to enter the club.

A bullet also hit a manager inside a neighboring bar.

Ashley L. Wilks, a 16-year-old from Portland, was killed. The other victim has not been identified, but Miguel Velasquez of the Peruvian Consulate in Seattle said she was a 17-year-old girl from Peru in an exchange program. He said her host family lives in White Salmon, Wash.

Both girls were part of a group of exchange students at The Zone to celebrate a birthday, said Chuck Itoh, chairman of the Rotary District 5100 exchange program.

Wilks was getting ready to leave for her vacation trip.

Wilks’ stepfather, Randy Thiesen, told The Oregonian: ‘‘We’re just shocked. We’re not doing good.’’

One shooting victim was in critical condition Sunday, and four others were hospitalized but expected to survive; two were treated and released.

Scott Bieber, the youth protection officer for the exchange program, said four of the wounded were exchange students from Ecuador, France, Guatemala and Taiwan.

‘‘Our hearts and our sympathies, thoughts and prayers go out to the victims’ parents for their loss,’’ Bieber said. ‘‘But it just kind of makes it harder to fathom when the whole purpose of this program is to foster peace and goodwill and understanding around the world.’’