shocked students stare,shake their heads,pull out their cell

shocked students stare,shake their heads,pull out their cell phone cameras and some can't help asking " Is that a horse?"
帮我分析下句子的结构：
如何解析这句话的结构，是否是shocked students stare,shake their heads,pull out their cell phone cameras 与 some can't help asking " Is that a horse?"两个完整的句子由连词“and”连接
shocked students stare,shake their heads,pull out their cell phone cameras 这一句完整的句子里的 stare ,shake ,pull out,这三个动词并列的话，为什么最后一个动词词组pull out 前面不加and。