What can be done if he told the arresting officer that my husband was helping him take the parts?

Your husband needs to hire a private criminal defense attorney who will investigate the facts in the case, and represent him.

There is a theory of prosecution (the "principal" theory) that would give the State Attorney's Office the option of charging anyone who may have known about the thefts and did something to assist or encourage it. For instance, if your husband is accused of assisting the theft by looking the other way or leaving a door unlocked then it is possible he could be charged with the crime along with the employee that was actually committing the theft. It is likely that your husband will be contacted by law enforcement regarding the employee's accusations. It is critical that he does not speak with law enforcement before speaking with an attorney about the situation.