Panic (cpu 2 caller

Yesterday the Photos application in my macbook closed because of an error and said I couldn't open it because of that error, so I restart my computer but it last all day without actually beginning. So at night I forced it to turn off. Today I tried to use it but this appeared:

"Your computer restarted because of a problem. Press a key or wait a few seconds to continue starting up."

Then the Apple's symbol appeared, as it always does when the computer is starting up, with a message in the corner:

panic(cpu 3 caller 0xffffff802a9bd555): "Process 1 exec of /sbin/launchd failed, errno 8"@/SourceCode/xnu/xnu-2782.28.48/bsd/kern/kern_exec.c:4867

Debugger called: <panic>

Backtrace (CPU 3), Frame : Return Address

0xffffff809d593df0 : 0xffffff802a52bda1

0xffffff809d593e70 : 0xffffff802a9bd555

0xffffff809d593ef0 : 0xffffff802a997752

0xffffff809d593f10 : 0xffffff802a9d9a71

0xffffff809d593f50 : 0xffffff802a5282d6

0xffffff809d593f80 : 0xffffff802a61843e

0xffffff809d593fa0 : 0xffffff802a634b3f

BSD process name corresponding to current thread: init

Mac OS version:

Not yet set

Kernel version:

Darwin Kernel Version 14.3.0: Mon Mar 23 11:59:05 PDT 2015; root: xnu-2782.20.48~5/RELEASE_X86_64

Kernel slide: 0x000000002a200000

Kernel text base: 0xffffff802a400000

__HIB text base: 0xffffff802a300000

System model name: MacBookPro9,2 (Mac-6F01561E16C75D06)

System uptime in nanoseconds: 2573490822

AppleUSBMultitouchDriver: :checkStatus - received Status Packet, Playload 2: device was reinitialized

It then turns off and start up again and a different code shows. Sometimes it beggins with "panic(cpu 2 caller" or "panic(cpu 0 caller", and different numbers. It changes 4 times before showing this symbol: and finally turn off. And all this happened every time I tried to start up my macbook.

I don't know what to do, please help me.

sorry for my english.