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It looks like you may have answered your own question here, because with this particular question there is no debate among lawyers as to what the answer should be. Your friend needs needs to get counsel and to stop answering questions. If he is answering questions, then he is giving them proof. The fact that they are still questioning him means that whatever he is saying isn't helping him. He's a suspect, and he has a Constitutional right to remain silent. He doesn't have to give evidence against himself and anything he does say or has said can be twisted by the police and used against him.
If he doesn't cooperate with the authorities, the police may have enough evidence to arrest him anyway. But at least he won't be handing them more evidence to be used against him. And typically, when the police have enough evidence to charge someone with, they just make the arrest. They don't come looking to question the suspect. So keeping his mouth shut from here may make all the difference in the world when it comes to being charged.
Finally, if he has not been charged with a crime yet, while it's a great time to find a lawyer he may want to use in the worst case scenario, he does not actually have to hire one now, since there's nothing for that lawyer to do. But by consulting with a lawyer and having the name and number of one that he likes, he'll be in good shape if it turns out that he is ever arrested. He won't have to waste precious time without counsel and there will be a lawyer already up to speed on his case waiting in the wings who can step right in when called upon.