(CNN) -- A man accused of shooting into a crowd outside an under-21 nightclub -- killing two teenage girls and wounding seven other people -- before shooting himself was in critical condition Monday, police in Portland, Oregon, said.
A shooting outside a Portland nightclub Staurday killed two people and injured seven others, police said.
Investigators identified the gunman in Saturday night's shooting in Portland as Erik Salvadore Ayala, 24, and are trying to determine why the rampage happened, police said.
"This is unprecedented in the city of Portland. We don't have this type of thing," Portland police Detective Mary Wheat said, adding that even seasoned police veterans were shocked by what she called "a random act of violence."
"Nobody knows the motive at this time," Wheat said, noting that Ayala didn't have a police record. "We're trying to figure what drove him to this."
Investigators believe Ayala sprayed bullets into a crowd of students outside a non-alcohol nightclub called The Zone on Saturday night and then shot himself, authorities said.
The students were participants in a Rotary Club foreign exchange program. Slain were Ashley Wilks, 16, and a Peruvian exchange student, Marta "Tika" Paz De Noboa, 17, according to Wheat.
Wilks, a Portland high school sophomore, was getting ready to spend her junior year in either France or Spain, her principal said.
Two juveniles, four 18-year-olds and a man in his 40s were wounded, Wheat said, adding that exchange students were among those hurt.
Scott Bieber, youth protection officer for the exchange program in northern Oregon and southwestern Washington, said the shooting was "nothing like anything we've ever seen in Rotary before, to have as many of our kids involved in something as tragic at one time."
"Our main focus right now is to build a support structure for the students who were involved and their host families and their real families, and also for the families of the 28 other inbound students we have in our Rotary district," Bieber said.
Eleven exchange students went to the club to celebrate a birthday and were waiting in line when the assault began, Bieber said.
Wheat said a 9 mm handgun was used in the shooting.
"It doesn't appear at this time that he reloaded," she said.
Paz De Noboa was attending Columbia High School in White Salmon, Washington. School officials were helping students deal with their grief over the incident, and counselors were available, said Superintendent Dale Palmer and Vice Superintendent Jerry Lewis of the White Salmon Valley School District.
"She was very shy and reserved," Palmer said. "I think she was a good student and helpful to other struggling students."
Matt Utterback -- principal of Ashley Wilks' school, Clackamas High School -- issued a statement on the school's Web site confirming Wilks' death and the wounding of Susy De Sousa, an 18-year-old foreign exchange student from Italy.
Wilks' was a "bright and curious student" who took honors classes and was a member of the swimming team, Utterback said. He passed along praise from her teachers and her swim coach.
"An awesome student with a beautiful smile. She was the kind of person that lights up a room. A truly wonderful, delightful kid," Utterback said.
About De Sousa, Utterback said: "Susy challenges herself to take rigorous classes despite the fact that English is her second language. She has a good sense of humor and is known for her persistence."
De Sousa was in critical condition but improving, Wheat said.
Classes were not in session Monday because it was a teacher workday. Utterback said counseling was available for students, and deplored the shooting.
"Such a horrific act is impossible to accept or understand," he said.