Jim Van Horn said he was a frequent patron at Orlando's Pulse night club. He said another "regular" at the Florida gay bar was Omar Mateen, the man who killed 49 and wounded dozens more early Sunday.
Speaking to The Associated Press late Monday, 71-year-old Van Horn says he saw Mateen trying to pick up men at the club.
Van Horn said he met Mateen once. He said the younger man was telling him about his ex-wife.
Van Horn says some friends then called him away and told him they didn't want him talking to Mateen because "they thought he was a strange person."
Despite Mateen's pledge of support to the Islamic State group, other possible explanations emerged, including questions of whether he was conflicted about his sexuality.
His ex-wife said he suffered from mental illness. And his Afghan-immigrant father suggested he may have acted out of anti-gay hatred.