Perhaps there is something in his background that made him a target?
Wicker committees
Wicker serves as Deputy Whip and is a member of the Armed Services Committee; the Budget Committee; the Commerce, Science, and Transportation Committee; the Environment and Public Works Committee; and the Joint Economic Committee.
A list of legislation he has recently sponsored is listed
http://thomas.loc.gov/cgi-bin/bdquer...cker,+Roger%29
Nothing in his legislation that is especially controversial.
He does not have a very good record of sponsoring legislation that becomes law. Last three Congresses 0.0% of his bills became law
According to Opencongress.org he votes with the party 88% of the time. Nothing special there either.
Does not look like there is anything especially "target worthy" in his Senatorial duties.
Could always be a personal issue. Never know about them senators.