A Pennsylvania newspaper is apologizing for running an ad calling for the assassination of President Obama.

In the Thursday edition of The Warren Times Observer, the paper ran a personal ad that read, "May Obama follow in the steps of Lincoln, Garfield, McKinley, and Kennedy." Each of those presidents was assassinated.

The publisher of the paper told the Associated Press that the paper didn't originally realize the meaning of the ad, and the Times Observer apologized for the oversight in Friday's edition.

The Secret Service is reportedly investigating the incident.

Here's a snapshot of the ad: