Always hard to be certain, but this is probably a hawthorn. Crataegus sp. Have you noticed any thorns on it, or clusters of flowers or fruits? Leaves are quite variable among the species, and sometimes even on a given shrub.
Thanks Thanrose. I know nothing about hawthorn's and have not seen them with red leaves during my research. But you might be right. I see no thorns or clusters of fruits. It's a small baby tree/ shrub too. Here is another better pic of it when I got home and potted it:
