Jay Cutler dropped back but held the ball a bit too long before being hit from his right by Ndamukong Suh.
Sack, fumble, Detroit touchdown.
Another mistake for Cutler — and this one put Chicago in a hole the Bears couldn't climb out of.
Cutler threw three interceptions in addition to his costly third-quarter fumble, and the Bears lost for the first time under new coach Marc Trestman, falling 40-32 to the Lions on Sunday. Chicago trailed 40-16 late in the game before scoring twice to make it close.
"Whenever you give up those kinds of turnovers, it's hard," Cutler said. "Three picks and a fumble — it's hard to come back from."
Reggie Bush's 37-yard touchdown run highlighted a 27-point second quarter for Detroit. He accounted for 173 yards of offense.
Cutler threw for 317 yards and two touchdowns, but the turnovers were costly. The Bears (3-1) were also 1 for 13 on third down.
"We've done well on third down the last three weeks. We did horribly today," Trestman said. "That starts with me. I've got to do a better job."
Detroit (3-1) moved into a first-place tie with Chicago in the NFC North. The Lions scored 24 straight points, including three touchdowns in a span of 3 minutes, 26 seconds, after Matt Forte's 53-yard TD run gave the Bears a 10-6 lead early in the second quarter.
Cutler threw a pair of touchdown passes and 2-point conversions to pull Chicago within eight points and make the score look respectable. Lions receiver Kris Durham recovered an onside kick in the final minute to seal the win.
"There are no moral victories, but I thought our guys played tough for the last 30 minutes of that game," Trestman said. "I know as a staff we appreciate that."
Cutler's first interception came in the first quarter, but the Bears recovered from that and took the lead on Forte's long run. Detroit answered with a field goal, then went ahead 16-10 when Matthew Stafford tried a quarterback sneak from the 1-yard line, appeared to lose the ball, then got it back for a touchdown.
Cutler immediately threw another interception, and Glover Quin returned it 42 yards to the Chicago 2-yard line. Stafford threw a 2-yard TD to Calvin Johnson.
Bush burst through a huge hole and hurdled safety Major Wright to give the Lions a 30-10 lead.
Stafford completed 23 of 35 passes for 242 yards. He did throw an interception, and his fumble late in the first half helped Chicago add a field goal to make it 30-13 after two quarters.
The Bears kicked another field goal midway through the third quarter to pull within two TDs, but Cutler hurt the Bears when his up-for-grabs pass was picked off by safety Louis Delmas, who had two interceptions.
"Although he's a great quarterback with a strong arm, sometimes we can read him and we got the better of him," Delmas said.
Cutler said his mistakes were physical, not mental.
"I felt good about my decision making," he said. "I just missed some throws."
Stafford turned the ball over again when his low pass intended for Johnson deep in Chicago territory was kicked up in the air and intercepted by Wright.
But Suh sacked Cutler and forced a fumble fellow defensive tackle Nick Fairley recovered and returned 4 yards for a score that put Detroit up 37-16 late in the third period.
Cutler went 27 of 47. He threw a 14-yard TD pass to Alshon Jeffery with 4 minutes left, and a 2-point conversion pass to Jeffrey pulled Chicago within 16 points.
Cutler threw a 10-yard TD pass to Earl Bennett with 43 seconds to go and connected with Brandon Marshall for a 2-point conversion that made it 40-32.
"I watched the demeanor of our football team on the sideline during the last 30 minutes of the game," Trestman said. "I thought it was excellent. Guys were fighting, guys were in it. They were focused. There was a sense of urgency there."
NOTES: Forte finished with 95 yards on 14 carries. ... Lions CB Rashean Mathis left the game in the first half with a concussion and didn't return.
AP NFL website: www.pro32.ap.org