Help! Thief!

This little old lady was robbed of her purse in Chambéry on Monday. The thief nearly ran into me as he darted out of the dark arched entry and raced across the road before disappearing down an alleyway. Roger and I were spending the day in Chambéry, so that we could discover the centre of the old city, where the pedestrian streets are narrow and charming old dwellings crowd into winding lanes. We expected to experience the ambience of the old town in a far more pleasant way than what we did.
We hardly caught a glimpse of the thief as he skipped to avoid us and darted away. I recall thinking at the time that it would be the sort of thing a thief would do, but it was not until we saw the lady searching through her shopping bag and then look up with such a distressed look, wailing "Oh! No!No!N0!" that we realised he actually was a thief. He had knocked her against the wall before running off with her purse, which must have been visible in her shopping bag - it was so full that the zip wouldn't close.
I couldn't understand much of what she was saying. I think she started speaking in Italian, or maybe French with such a strong Italian accent that most of the time I couldn't understand anything. But in some situations you don't need words...
Roger helped her to look for her purse, in case it had been discarded down the alley as the thief fled. Then, finding nothing, we accompanied her back to the building where she lived. Her keys had been in the stolen purse, so she couldn't get in. She tried ringing a neighbour's doorbell but there was no answer. Soon after a young lady who lived in the same building opened the door so she could get in, but still she would not be able to get into her own apartment. We explained what had happened, and the young lady was happy to invite the poor old lady in and to take over.
So what did the thief look like? Roger thinks he was young and fast. I noticed he had dark hair and a shirt with vertical stripes in a light colour. And I wonder how many other people he robbed that day...