I thought Obama was dead
What is your reason for thinking that obama was dead?
I heard he was assassinated in a radio news segment
Unfortunately, not everything on the radio is true. If you are unsure whether or not a radio program is correct, you should look up the information on line.
You should be able to confirm on line.
Just be careful with the sources you choose to trust. You never know what someone is going to claim online, so you are better off just checking the facts yourself or looking at multiple sources.