Following Tillman's touchdown, the Jaguars allowed consecutive scoring drives after playing stout defense in the first half.
Jay Cutler hooked up with rookie Alshon Jeffery for a 10-yard score on the first play of the fourth quarter and found Brandon Marshall for a 24-yarder with 8:37 remaining in the game.
Lance Briggs returned another interception for a score after that, a 36-yarder that made it 34-3.
"It just snowballed," cornerback Rashean Mathis said.
Cutler completed 23 of 39 passes for 292 yards, with two TDs and an interception before giving way to backup Jason Campbell.
Marshall caught 12 passes for 144 yards. Forte, who has one touchdown this season, ran 22 times for 107 yards.
Few outsiders gave the Jaguars a chance before the game. The only thing that seemingly was in Jacksonville's favor was catching Chicago on a short week. The Bears got home from Dallas early Tuesday and were back on a plane Saturday.
That may have contributed to Chicago's slow start. But it mattered little in the second half — thanks mostly to the interceptions.
"No one feels worse than we do," Mathis said. "We're not producing the way we should be."
NOTES: Tillman became the franchise's all-time leader in defensive touchdowns with eight. ... Jeffery left the game with a hand injury. ... Jaguars PK Josh Scobee tied Mike Hollis for the most FGs (175) in franchise history. ... Jones-Drew became the third player in team history to eclipse 12,000 all-purpose yards, joining Fred Taylor and Jimmy Smith.
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