Paris ( CNN ) A man with a handgun entered a post office outside of Paris early Friday afternoon before reportedly surrendering and releasing his hostages unharmed . The incident in Colombes , a community about 10 kilometers northwest of the French capital , began at about 12:45 p.m. ( 6:45 a.m . ET ) and was over two hours later . The gunman might be mentally unstable , according to police in Colombes . Police said that they do n't know yet whether the incident is related to terrorism . This is a hot topic in France after last week 's deadly attacks . A Western intelligence source said there could be as many as 20 terrorist sleeper cells of between 120 and 180 people ready to strike in France , Germany , Belgium and the Netherlands . The gunman eventually surrendered and the hostages emerged with no injuries , according to France Bleu , which is part of the country 's public broadcasting group . CNN 's Greg Botelho and Elwyn Lopez contributed to this report .
Public radio : Gunman surrenders , is released uninjured . He visits a post office in Colombes , which is just outside Paris . Police : The man may be mentally unstable .