When Carter Ellis woke up to an explosion and saw smoke seeping through the front door, he put on clothes and ran out of his friend’s apartment building without shoes.Ellis, a sophomore musical theater major, was staying at his friend’s apartment building overnight on 521 Zulema St. in Oakland when a five-alarm blaze erupted Friday morning.No one in the three-story building was hurt, according to the Pittsburgh Bureau of Fire. The fire started around 7:47 a.m. because of an electrical junction box and also involved 519 Zulema St. Firemen were on the scene until 9 p.m., said the Bureau.Damage is estimated to be $350,000 according to the Pittsburgh Bureau of Fire.Ellis said the blaze lasted about two to three hours.The explosion Ellis heard turned out to be a fire escape falling and clanking metal together. Ellis left with his phone, but without his backpack containing textbooks and notes from the school year. He said he would ask the University to replace the textbooks.Ellis’s friend, a University of Pittsburgh student who lived on the second floor, was at swim practice during the incident. He lost almost all of his belongings.“I have never been more startled waking up to an explosion in my life,” said Ellis over the phone Monday. “Thank goodness everyone is OK.”