Camera moves and then starts rotating

Dears, I am trying to do a certain animation of the camera to show a logo.
The camera should start at the ground level (z=0) and move through the logo and along a path (x,y) until a certain time t_1.
After t_1 the camera should start to rotate gradually until, at the end of the rotation it points exactly to an empty object.
I have tried with follow path but I have no idea how to instruct blender to start rotating the camera after a certain keyframe.

Thanks for your help.