Clinton pushed regime change in Libya, and pushed it hard.
Check it out:

On Sunday, the world watched in horror as a migrant ship from Libya carrying 950 people sank in the Mediterranean, with photographs of floating bodies making their way across the wires.

According to The New York Times:

Warmer spring weather has unleashed a torrent of smuggler boats, mostly from Libya, bearing migrants and refugees from the Middle East and Africa, often fleeing war and poverty for a foothold in Europe.

Reports state that the smugglers locked migrants in the hold.