Police say the shooter was in custody, and was identified by people familiar with the investigation as Jared Loughner, 22. U.S. officials who provided his name to the AP spoke on condition of anonymity because they were not authorized to release it publicly.

His motivation was not immediately known, but Dupnik described him as mentally unstable. Later Sunday, authorities ruled out any possible involvement by a man who had been described earlier as a “person of interest.”