Nexus 5 with Android M Preview 3 isn't turning on

Hello.

I installed (via apk) a new Google Play Services version on my N5, the Google Play Services kept crashing every 10 seconds. I tried to reboot it to bootloader by holding down all 3 physical buttons but I let go of one to soon. The device turned on immediately and I immediately repress the button I had released just after the device turned on. Now my N5 is off and won't turn on. Please help!