HOUSTON – Police are asking for the public's help as they search for a man seen on crutches just before he robbed a store in northwest Houston with a knife.

Investigators say the man walked into the store on 13200 Northwest Freeway, and was seen putting items in his backpack as he made his way around the store on crutches.

When the man tried to leave the store without paying, several employees tried to stop him, but he pulled out a knife and started waving it at them.

The man was seen getting into the passenger seat of a blue or gray Volkswagen Touareg before taking off.

If you know anything about the man, you're asked to call Crime Stoppers at 713-222-TIPS.

A $5,000 reward is being offered.