Jessica Johnson woke to the sounds of screaming but thought it was just a Cubs fan straggling home late from Wrigley Field six blocks away.



She went to the window anyway. "He was yelling, 'Get out. Get out. Get out,' " said Johnson, who dressed, grabbed her keys and ran outside barefoot.



"Once in the front, I saw flames shooting out of the side of the building," she said. The man she heard yelling was on the sidewalk, bleeding. Neighbors were running outside and calling 911.



"It was scary, terrifying," she said.



Two people inside the three-story apartment building in the 3400 block of North Janssen Avenue in Lakeview jumped to safety and two others were rescued by firefighters, according to Deputy District Fire Chief John Shehan. All four were taken to hospitals in serious-to-critical condition.



The fire started about 1:50 a.m. in a rear apartment on the third floor of the six-unit building, Shehan said at the scene. The Fire Department was initially called to an address in the 3400 block of North Southport Avenue, a block east. Shehan said firefighters lost a minute or two while searching for the building that was on fire until they got a second call with the right address.



"A minute or two (can make) a big difference," Shehan said. "There was a lot of fire venting from the apartment."



The building sustained moderate damage, he said.



A 22-year-old man and a woman, whose age was not available, were taken to Advocate Illinois Masonic Medical Center, police said. A 35-year-old man and a 23-year-old woman were taken to Northwestern Memorial Hospital, police said.



Johnson shook slightly as she stood on the sidewalk across from her home where firefighters continued to search for hot spots early Friday. She wrapped a white sheet around herself and was wearing flip-flops she grabbed from her car parked nearby.



She said a firefighter brought out her cellphone from her apartment. "I kind of came out in a panic," she said, adding that she called her mother right away to let her know she was all right.



Johnson, who has lived in the building for about a year, said she was told her apartment had some smoke and water damage.



A woman who lived in the house next door came up to Johnson to offer help and exchange phone numbers.



"I can't even remember how to use my phone," Johnson said, waiting a second to take down the woman's number.



"If you need any help, let me know," the woman said.



"Thank you," Johnson replied.



Gavin Blasczyk, 23, who lives on the first floor of a three-story red brick building next door, stood barefoot outside along with other neighbors. He said one of his four roommates woke him and others after hearing screams outside.



"I didn't really understand it at first," he said. "It was kind of crazy to walk outside and see the flames."



Blasczyk said he ran out to see a woman who jumped out of the burning building onto the roof of his building's garage. She was wrapped up in blankets and had bruises, he said.



He said he climbed onto the roof and helped her down to the ground where first responders took her.



"There was a lot of adrenaline," he said.



The cause of the fire was under investigation. The police Bomb and Arson Unit was inspecting the site as part of standard procedure.