INDIANAPOLIS -- A 2-year-old boy was hospitalized in serious condition Wednesday after he fell from an apartment house's third-floor window on the city's east side Tuesday evening, authorities said.

Joshua Carter Jr. was playing in a bedroom at 544 Woodruff Place Middle Drive with his 6-year-old brother and had climbed onto a radiator when a window's glass broke, perhaps because Joshua was pushing against it, police said.

His father heard the glass and rushed upstairs in time to see Joshua fall headfirst from the window at about 6:30 p.m., Indianapolis police Lt. Jeffrey Duhamell said.

"When he heard the glass, he knew something was wrong. He ran in there and he heard the other child saying, 'Get away from there,'" Duhamell said. "There was no glass inside. It was all on the outside."

Joshua fell onto a concrete sidewalk. He was unconscious when people in the area rushed to his side, 6News' Rick Hightower reported.

"Just broken glass and blood and people just freaking out," said Sue Wolcott, who lives nearby. "There wasn't much we could do to help."

Joshua was taken to Methodist Hospital, where his condition was upgraded from critical to serious.

Police said that they think Joshua struck a gutter on the way down, which possibly slowed his descent.

Joshua, his father and his brother live in the house, which is divided into four apartment units.