为什么是原型?he saw two thieves rush out of a shop and run towards

see sb doing sth 和see sb do sth是固定搭配,没有跟过去式搭配的用法
see sb doing sth 是强调看见某人正在做某事,着重动作过程, 而see sb do sth 是看见某人做某事,着重于看见这件事的发生.
如：I saw him drawing by the river then.
我见他那时正在河边画画．
I saw him draw by the river sometimes
我看见他有时在河边画画．